Similar to heart disease and diabetes which are "diseases of civilization" or "Western diseases" (Trowell and Burkitt, 1981) that have attained high prevalence in urban society because of environmental factors rather than "genetic deterioration," an epidemiological transition (Omran, 1971) in occlusal health accompanies urbanization.In other words, the reason observational studies in affluent nations haven't been able to get to the bottom of dental/orthodontic problems and chronic disease is that everyone in their study population is doing the same thing! There isn't enough variability in the diets and lifestyles of modern populations to be able to determine what's causing the problem. So we study the genetics of problems that are not genetic in origin, and overestimate genetic contributions because we're studying populations whose diet and lifestyle are homogeneous. It's a wild goose chase.
Western society has completely crossed this transition and now exists in a state of industrially buffered environmental homogeneity. The relatively constant environment both raises genetic variance estimates (since environmental variance is lessened) and renders epidemiological surveys largely meaningless because etiological factors are largely uniform. Nevertheless most occlusal epidemiology and heritability surveys are conducted in this population rather than in developing countries currently traversing the epidemiological transition.
That's why you have to study modernizing populations that are transitioning from good to poor health, which is exactly what Dr. Weston Price and many others have done. Only then can you see the true, non-genetic, nature of the problem.